import java.util.Scanner;

public class demo1 {
    public static int fib(int n) {
        if(n==1||n==2) {
            return 1;
        } else {
            return fib(n-1)+fib(n-2);
        }
    }
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n=scanner.nextInt();
        System.out.println(fib(n));
    }
}
